<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    /* 清除默认样式 */
    * {
        padding: 0;
        margin: 0;
        list-style: none;

    }

    .list {
        width: 200px;
        height: 200px;
        margin: 100px auto;
        transform: rotate(0deg);
    }

    li {
        width: 100px;
        height: 100px;
        background-color: yellow;
        float: left;
    }

    li:first-child,
    li:last-child {
        border-radius: 0px 200px 0px 200px;
    }

    li:nth-child(2),
    li:nth-child(3) {
        border-radius: 200px 0 200px 0;
    }
</style>

<body>
    <!-- 
        需求：风车 自动旋转  想停止就能停止

     -->
    <ul class="list">
        <li></li>
        <li></li>
        <li></li>
        <li></li>
    </ul>
    <button id="rotateBtn">转起来</button>
    <button id="stopBtn">停下来</button>
    <script>
        /* 今晚总结获取元素的六种方式
        写纸上

        */
        console.log(rotateBtn);
        var list = document.querySelector('.list');
        var rotateBtn = document.querySelector('#rotateBtn');
        var stopBtn = document.querySelector('#stopBtn');
        var num = 0;
        var timer;
        rotateBtn.onclick = function () {
            // clearInterval(timer);
            // 转起 循环定时器走了
            timer = setInterval(function () {
                num++;
                list.style.transform = 'rotate(' + num + 'deg)';
            }, 30)
        }

        // 停止 定时器清除了
        stopBtn.onclick = function () {
            clearInterval(timer);
        }


    </script>
</body>

</html>